1. Field of the Invention
This invention relates in general to a system for generating steam downhole in oil wells, and in particular to a packer and electrical connector apparatus used with a steam generator.
2. Description of the Prior Art
Steam is used in some cases to facilitate the production of oil from reservoirs having very viscous crude. In the prior art, steam is generated at the surface and pumped down tubing in injection wells. The steam will flow through perforations in the casing of the injection well to heat the crude and force it to flow to producing wells.
One disadvantage of steam injection systems is the energy loss which occurs as the steam cools while being pumped from the surface down to the perforations. This is particularly a problem in deeper wells.
Proposals have been made to pump water down the well and generate the steam downhole. This would avoid the heat loss that occurs while the steam is being pumped down the well in conventional systems. The downhole steam generator would generate the steam using high voltage electrical power supplied through electrical cable extending down into the well. A packer above the steam generator would prevent the steam from flowing back up the annulus of the well.
One problem presented by a downhole steam generator is providing the electrical connections. Conventional downhole electrical connections are unable to withstand the high temperatures at the voltage and power levels required. The power requirements for a downhole steam generator are high, up to 7200 volts and 240 amps. The temperatures are high, possibly exceeding 600 degrees F.
Packers are available that have feed through mandrels for electrical wires to be connected for purposes other than downhole steam generators. The feed through mandrel is located to one side of the main conduit in the packer for the tubing. The feed through mandrel has insulated conductor rods extending through the packer. The lower end of the upper section of the cable is connected to the upper end of the connector rod. The upper end of the lower section of cable below the packer is connected to the lower end of the conductor rod.
The conventional feed through mandrel would not be acceptable for use in a downhole steam generator system. The high temperatures would cause deterioration of the elastomeric insulators in the feed through mandrel. Also, the feed through mandrel has a rather small diameter, necessitating that the three conductors from the power cable be spaced quite close to each other. This results in the possibility of insulation failure between the conductors because of the high voltage.